Halide brines, particularly sodium chloride and other alkali metal and alkaline earth metal salts such as calcium chloride and magnesium chlorides, are used extensively for inhibiting snow and ice accumulations on a variety of outside surfaces including such uses as deicing, melting snow and freeze conditioning of roadways, paved areas, bridges and the like as well as for surfaces of bulk materials, coal and minerals for example. They are also used for dust control on similar surfaces such as paved and unpaved roadways, especially during dry weather, and during the handling and transportation of dust-producing bulk materials, such as coal or other materials.
Aqueous solutions of these halides are known to corrode metals and cause scaling or surface damage to concrete. For example, heavy use of road deicers can result in serious damage to autos and other vehicles as well as rapid deterioration of metal reinforcing rods in poured concrete roadways and bridges. The halides used for dust control and for freeze conditioning of bulk materials such as coal or other minerals often cause corrosive deterioration of the materials-handling equipment, rail cars and other container carriers.
The need for corrosion inhibitors designed for deicing and snow control is well known. Chromates, phosphates, zinc salts and nitrites have been used to provide varying degrees of corrosion inhibition for halide brines. Nitrites have been noted only to change the nature of corrosion from general to localized, causing possible perforation in metals in very short time. Chromates, zinc salts and phosphates have come under increasing scrutiny due to environmental concerns.
U.S. Pat. No. 5,531,931 teaches the use of a deicing composition comprising a deicing salt and corrosion-inhibiting water soluble rare earth salt and/or a water-soluble organic acid salt. A deicing composition and method comprising by-products from a wet milling process of corn is disclosed in U.S. Pat. No. 5,635,101. A process for deicing a roadway surface comprising adding to a snow or ice covered roadway surface an effective amount of a composition consisting essentially of a lignosulfonate and metal chloride salt is taught in U.S. Pat. 4,668,416. U.S. Pat. No. 5,118,444 discloses use of an amine oxide surfactant blended with an agriculturally acceptable pesticide to reduce irritation to animals and corrosiveness to materials, the use of a liquid deicing composition comprising magnesium chloride and an organic inhibitor selected from the group consisting of triethanolamine, triethanolamine acid salts, citric acid, metal salts of citric acid and mixtures thereof was disclosed in U.S. Pat. No. 5,302,307.
There is a need, however, for a method for applying an environmentally acceptable, easy to use, deicing and freeze conditioning aqueous halide to outdoor surfaces without extensive metal corrosion or damage to cement structures. There is also a need in the art for a method of applying halide brines with improved corrosion-inhibition properties adapted for addition to otherwise conventional dust control compositions.